The present invention relates to an electrophotographic image forming device provided as a copying machine, a printer, and/or a facsimile, etc., so as to transfer a toner image onto a sheet of paper. More particularly, the present invention relates to an image forming device appropriately provided as a tandem type color image forming device using a plurality of kinds of toner.
In the tandem type image forming device, toner images are transferred onto a sheet of paper by the following method.
First, a plurality of image bearing elements bearing respective toner images are located in order from one side to the other side of the main unit of the device. Then, a sheet of paper sequentially passes through the respective image bearing elements, with being supported by a transfer and transport bearing element. With this structure, in the tandem type image forming device, a plurality of kinds of the toner images constituting a color image are transferred onto the sheet of paper.
Conventionally, in an image forming device of such a system, the transfer and transport bearing element is lowered and separated from the image bearing elements by opening a front or a side door of the device and then operating a lever, etc., provided in the device. This operation is performed when a sheet of paper is abnormally stopped between the image bearing elements and the transfer and transport bearing element due to transport failure, etc., or at the time of maintenance to replace a process unit which includes an image bearing element and image forming means placed in the surroundings of the image bearing element.
In order to eliminate the foregoing lever operation, for example, (1) the U.S. Pat. No. 4,873,541 (published on Oct. 10, 1989) discloses a method in which the opening of a door of an image forming device is detected, then transfer and transport means is electrically separated from image bearing means, which speeds up the handling of a paper jam.
In the foregoing conventional technique (1), when a paper jam is caused due to some power-down, there are some cases that the transfer and the transport means cannot be separated from the image bearing means although the door of the image forming device is opened, and a jammed sheet of paper cannot be removed.
Besides, in a general image forming device, when a door is opened, power to each part in the image forming device is cut off so as to prevent the operation of each part, which enhances safety. However, in the foregoing electric structure (1), if power is supplied in a condition that a door is opened for the handling of a paper jam, there is a problem that safety is declined.
It is therefore an object of the present invention to provide an image forming device with high safety, in which a transfer and transport bearing element is separated from an image bearing element in association with the operation of opening a door, even when power supply is cut off.
To achieve the foregoing object, an image forming device of the present invention, which is a tandem type, electrophotographic image forming device in which a plurality of image bearing elements bearing respective toner images are located in order from one side to the other side of the main unit of the device, and a sheet of paper sequentially passes through the respective image bearing elements with being supported by a transfer and transport bearing element, so as to transfer a plurality of kinds of the toner images onto the sheet of paper, is structured so as to include:
a transfer frame holding the transfer and transport bearing element;
a first separating/contacting mechanism mechanically lowering/raising the whole of the transfer frame in association with opening/closing of a front door of the main unit of the device, and separating/contacting the transfer frame from/with the image bearing elements;
a second separating/contacting mechanism mechanically lowering/raising a right side of the transfer frame in association with opening/closing of a right side door of the main unit of the device, and separating/contacting the right side of the transfer frame from/with the image bearing elements; and
a third separating/contacting mechanism mechanically lowering/raising a left side of the transfer frame in association with opening/closing of a left side door of the main unit of the device, and separating/contacting the left side of the transfer frame from/with the image bearing elements.
According to the foregoing structure, just by opening a door of the image forming device from a plurality of access directions, the transfer and transport bearing element, which is formed to be long from side to side, can be separated from the image bearing elements in association with the opening of the door, on a side opened. Consequently, to cope with various paper jams related to the transfer and transport bearing element, it becomes possible to handle a paper jam by opening/closing a door of the image forming device from the most appropriate direction. Besides, at the time of replacing a process unit, the replacement can be easily carried out by opening/closing a door which is appropriate for the replacement.
Since the opening/closing operation of the doors is mechanically converted to carry out separating/contacting operation of transfer and transport means, this structure enables the separating/contacting operation to be carried out even when power supply is cut off. Further, by arranging to cut off power supply when a door is opened, this structure can enhance safety.
Besides, in the image forming device of the present invention, the transfer frame holding the transfer and transport bearing element has support axes protruding from its four corners in a front-to-rear direction, and the image forming device is structured so as to further include:
holding plates each of which is swingably displaced about an axis line extending in the front-to-rear direction;
holding arms each of which raises/lowers each of the support axes by being swingably displaced about an axis provided on each of the holding plates;
holding levers each of which is swingably displaced about an axis provided on each of the holding plates, and has a long hole in which an axis provided on each of the holding arms is inserted with a clearance;
holding stays connecting lower parts of a pair of the holding plates provided in front and rear;
wedge-shaped link blocks located at the four corners of the transfer frame and inserted between a base of the main unit and the holding stays;
a link mechanism which extracts/inserts the link blocks in association with the opening/closing of the front door of the main unit of the device; and
driving members each of which separates from or contacts an end section of each of the holding levers on a side opposite to a side provided with the long hole, in association with the opening/closing of the respective side doors of the main unit of the device,
wherein the holding arms, the holding levers, the holding plates, the holding stays, the link blocks, and the link mechanism constitute the first separating/contacting mechanism, in which the link mechanism extracts/inserts the link blocks between the base of the main unit of the device and the holding stays in association with the opening/closing of the front door of the main unit of the device, lowering/raising the support axes at the four corners of the transfer frame together from the holding stays provided on the right and the left sides, via the holding plates, the holding levers, and the holding arms, and separating/contacting the transfer frame from/with the image bearing elements, and
the holding arms, the holding levers, the holding plates, and the driving members constitute the second and the third separating/contacting mechanisms, in which the driving members provided to the respective side doors of the main unit of the device separate from or contact the end sections of the holding levers on the side opposite to the side provided with the long holes, in association with the opening/closing of the respective side doors, lowering/raising the support axes of the transfer frame on the sides of the respective side doors via the holding levers and the holding arms, and separating/contacting the respective sides of the transfer frame from/with the image bearing elements.
According to the foregoing structure, the first through the third separating/contacting mechanisms can be specifically structured.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.